One set of cards underperformed in my testing, but the others...did fine...partially...
My concern comes from running crossfire...I'm still dealing with addition of the second card lowering DISPLAYED framerates. FPS goes up, for sure, but it seems very similar to 3870x2 behavior, and the dreaded "microstutter".
Example #1: Dragon Age: Origins.
One card, 3.6ghz Phenom2 quad, max settings, 8xAA, V-sync enabled. Flawless.
Lower cpu soeed until it shows as a bottleneck, reached @ 3.3ghz.
Add in second card, no other way to describe the problem...things "stutter" as they move across the screen(NPC's, projectiles, etc).
Increase cpu speed to 3.6ghz, stutter is less, but still noticible.
Now, should adding a second card add up to a worse playing experience? Would adding 300mhz cpu not be enough additional cpu power to deal with the extra driver overhead? Why is more needed, to get THE EXACT SAME playing experience?
Is it because the 4890's are running @ pci-e 1.1, rather than 2.0?
Sheesh, my sig is from 2006...lol @ opteron and X1900 scores...dual 4980 barely twice that '06 score(214xx)? LOLZ.